SCIENTIFIC INSTRUMENTS AND THEIR RELATED CORRESPONDENCE

ABSTRACT. The need for registering and detailing all information
relative to the history of astronomical instruments and any alterations
to, or restoration of, them is stressed. This article describes the
conditions under which both the historical scientific instruments and
their related documentation, where now available, are catalogued and
preserved at Armagh Observatory. As illustrative examples, we have
selected two items of equipment which were acquired at the time of the
foundation of the observatory in 1789.

1. INSTRUMENTATION

The historical astronomical and other scientific instruments and
equipment acquired by the Armagh Observatory during its two hundred years
of existence have been catalogued in an earlier volume of this journal
(McFarland 1990). Each instrument was given an identification number
and photographed. All documentation relevant to the instruments which
could be located either in the observatory collection of manuscripts, or
in published papers were analysed and placed in chronological order, as
far as could be ascertained. Inventories were produced from time to time
in the course of the observatory's history and these proved most useful.
One of the instruments, the Troughton equatorial telescope, is maintained
at constant temperature and relative humidity, to reduce the rate of
deterioration. The temperature is kept at 17C, and the relative humidity
between 50 - 60%.
In particular, any papers relating to the disposal, loss or modification
of the equipment were documented. A loans and repairs logbook is
maintained which indicates the movement of the instruments, either for
repairs or exhibition purposes.

2. DOCUMENTATION

Butler & Hoskin (1987) produced a listing of all the manuscripts in the
observatory archives covering the period from the 1780s until the year
1916, the year in which Dr J L E Dreyer resigned the Directorship. Many
of the MSS contain references to the instruments, including drawings, and
alterations to the equipment. The MSS were catalogued under topics such
as observatory government, finances, administration and observations.
It is most important that material of this nature, hand-written
notebooks, observation record books, reduction books and so on, are
copied. A major task undertaken was the microfilming of some of this
material; unfortunately the project was never completed. Again, where
possible, such material should be maintained at constant temperature and
humidity (T=16C and RH=55%) and stored in acid-free envelopes. It is
notoriously difficult to ensure that air-conditioning units are operating
correctly, so constant monitoring of their performance is essential. The
units must be calibrated periodically.

3. ILLUSTRATIONS

Figure 1 shows the equatorial telescope constructed by J & E Troughton of
London and which was erected in the west dome of Armagh Observatory in
1795. The telescope dimensions are 2-1/2 inch aperture objective, 3-feet
focal length. Figure 1(a) shows the manufacturer's drawing of the
telescope, mounting and piers (Maskelyne 1789, Troughton 1792). Figure
1(b) is a photograph of the telescope in its present condition.
It is recorded in the Astronomer's Annual Report for 1844, appended to
the Observatory Minute Book, 1820-1958, p.38 that: "The west Equatorial
while in the hands of Mr Troughton was injured by a frost which condensed
on it moisture charged with the Sulphurous vapours of the London smoke,
and spotted it all over" --- signed T R Robinson. Consequently, in the
middle of the nineteenth century, Robinson had the instrument painted to
prevent further deterioration. This paint was recently removed and the
instrument cleaned and laquered. Looking at this newly revealed brass
work, and seeing its fragile nature, Robinson's action in all probability
saved this fine specimen of eighteenth century craftsmanship. Figure 2
is the first page of Troughton's instructions for the adjustment of the
telescope (Troughton c.1790).

3.2 Earnshaw Regulator

The Astronomer Royal for England of the day, Revd. Nevil Maskelyne,
requested Thomas Earnshaw to construct a regulator for Armagh Observatory
and to make it as air-tight as possible. After some reluctance, Earnshaw
eventually agreed and Figure 3 shows the result -- Earnshaw's first long-
case clock. Some years later, Earnshaw wrote to the Astronomer at Armagh,
Revd. J A Hamilton, asking him to provide testimonials for the two
regulators he ultimately provided for Armagh for publication in his
famous "Appeal to the Public" claiming originality in the design of his
time pieces. Figure 4 is a reproduction of Earnshaw's letter to Hamilton
(Earnshaw 1807).

4. CONCLUSION

In summary, it is vital to catalogue an observatory's scientific
instruments and their associated documentation for ease of retrieval for
the use of science historians. Master copies of manuscript holdings
should be made and any further copies required should be made from these
masters. The MSS should be stored at appropriate constant temperature and
humidity in acid-free envelopes. All movements of instruments and MSS
should be recorded in a logbook. Alterations and repairs to equipment
should be detailed as fully as possible. The instruments should be
photographed and an inventory formed. It is recommended that instruments
should be treated with extreme care.

ACKNOWLEDGMENTS

Dr C J Butler was responsible in large measure for initiating this
programme of restoration and conservation work at Armagh Observatory.
Mr M Murphy, the Starlink Manager at Armagh Observatory, has kindly
provided considerable help in coverting this document into a suitable
form for the World Wide Web. Armagh Observatory is granted-aided by the
Department of Education for Northern Ireland. It is a pleasure to
acknowledge the financial assistance received from the Friends of LISA II
which enabled the author to attend this IAU Technical Workshop.